This invention concerns automobile vehicle seats including hinge mechanisms connected in rotation by a connecting bar.
Such hinge mechanisms are currently used to make an adjustable connection which can be locked in position between the seat pan and the reclining backrest of the seat. These mechanisms can be of different types according to the principle used to control the backrest tilt angle adjustment.
Systems, especially called xe2x80x9ccontinuous hingesxe2x80x9d ensure both the locking in position and the adjustment, for example by a gear system installed inside a hinge mechanism housing and controlled by a rotary control knob installed on the side of the seat. Such systems are described for example in documents FR-2706380 and DE-4023824.
The hinge mechanisms are placed on the pivoting axis of the backrest in relation to the seat pan, on each side of the seat, between the seat pan framework flange and a backrest framework flange. These mechanisms conventionally include, as shown in FR-2706380, a housing attached for example to the seat pan flange, and a cup, installed so as to pivot on the housing and attached to the backrest flange. To ensure synchronisation of the control between the hinge mechanisms, these are, in a known manner, connected by a rigid synchro bar which can be coaxial with the mechanisms and the hinge axis of the backrest in relation to the seat pan or offset in relation to this axis as shown in DE-4023824.
The connection between the synchro bar and the hinge mechanisms can be rigid. For instance, the hinge mechanism which is located on the side of the seat where the backrest adjustment control is located includes a shaft protruding on each side of the mechanism, especially towards the outside of the seat, to install the control knob. The said synchro bar can then be welded to the other end of the shaft of the mechanism, opposite the control knob and oriented towards the inside of the seat. On the other side of the seat, the connection is generally ensured by a splined end on the bar or a drive square which engages into a splined hole or a corresponding female square in the hinge mechanism.
Due to various geometrical defects inevitable during the manufacture and the assembly of the frameworks of the backrest and the seat pan, exact coaxiality between the two hinge mechanisms is often not obtained. The pivoting axis of the backrest in relation to the seat pan is a geometrical axis passing via the centre of the two mechanisms, but the axes of each of the mechanisms themselves may be offset or form a slight angle between them. Also, the synchro bar may not be perfectly straight. The result is that during the controlled rotation of the bar, stresses are induced either in the hinges or in the links between hinges and synchro bar, and the stresses can vary according to the relative position of the seat pan and backrest framework flanges and therefore according to the backrest tilt angle. The functional clearance which may exist between the splined end of the shaft and the hinge mechanism in which it is fitted may allow a part of the above mentioned coaxiality defects to be absorbed but is however insufficient and substantial variations in the operating torque result affecting the flexibility of the backrest tilt angle control.
The aim of this invention is to solve this problem and to provide a hinge system the control of which is as light as possible that is with a torque as low and as constant as possible without sudden variations or peaks during the operation.
With these targets in mind, the subject of the invention is an automobile vehicle seat including two hinge mechanisms each with a centre of rotation via which a common pivoting geometrical axis passes, the hinge mechanisms being connected in rotation by a connecting bar extending more or less coaxially with or parallel to the said pivoting axis characterised in that this connecting bar includes at least one flattened longitudinal zone to provide the bar in the said zone with increased flexibility in relation with the rest of the bar. Whereas the bar has a general circular section giving it bending characteristics determined by its dimensions and the material of which it is made, the flexibility of the bar in each flattened zone is considerably increased in the direction orthogonal to the general plane of the said flattened zone without necessarily affecting to a great extent the torsion strength of the said bar.
Thus, during its rotation and especially during the variation of the tilt angle of the backrest caused by the controlled rotation of the bar, the increased flexibility of the bar in the flattened zone provides an overall flexibility which in a way allows the coaxiality defects of the two hinge mechanisms to be absorbed and therefore reduces the stresses exerted on these mechanisms and therefore the rotation control forces.
This reduction in stresses is especially noticeable when, preferentially, the bar includes several flattened zones, offset axially along the bar and in different angular planes around bar axis. According to a specific arrangement, the bar includes two flattened zones, offset axially along the bar and with different orthogonal planes. The combination of the flexibilities of the flattened zones acts then in the same way as a universal joint connecting the parts of the bar located axially on either side of the flattened zone facilitating the rotation of the bar when the coaxiality defects of the articulation mechanisms cause the connecting bar to bend.
According to a specific arrangement of the invention, the bar consists of a tube and the flattened zone or zones are formed by crushing the said tube, the section of the material in the flattened zone remaining the same as in the rest of the bar. Preferentially, the flattened zone includes a hole, drilled more or less in the centre of the flattened zone, perpendicular to the general plane of the said flattened zone. The section of the bar at the hole is then reduced and increases the flexibilityxe2x80x94the larger the hole the greater the flexibilityxe2x80x94but without however significantly reducing the torsion strength characteristics. In other words, the hole allows a high increase in the flexibility of the rotational control without significantly reducing the transmissible torque.
In common practice, the hinge mechanism located on the side of the seat including the manual control knob or lever itself includes a shaft one end of which accommodates the said knob or the said lever and the other end, facing towards the other mechanism, is solidly attached, for example by a weld, to an end of the connecting bar. In this case, the flattened zone or zones are located in the vicinity of the said end therefore in the vicinity of the most rigid section of the bar to limit as far as possible the displacements of the bar when it rotates with a coaxiality defect at its ends.